68 barracuda tire size question

Agree with 2 Darts -- 225 is too wide for a 5.5" rim, but you can confirm that by looking at the tire manufacturer's fitment chart. 215/70-14 is a good fit on that rim and looks aggressive. Your 215/75-14s seems a little on the tall side to me, although apparently they fit. A diameter in the 25.5 to 26" range might be ideal.